Tumor targeting by covalent conjugation of a natural fatty acid to paclitaxel.

Certain natural fatty acids are taken up avidly by tumors for use as biochemical precursors and energy sources. We tested in mice the hypothesis that the conjugation of docosahexaenoic acid (DHA), a natural fatty acid, and an anticancer drug would create a new chemical entity that would target tumors and reduce toxicity to normal tissues. We synthesized DHA-paclitaxel, a 2'-O-acyl conjugate of the natural fatty acid DHA and paclitaxel. The data show that the conjugate possesses increased antitumor activity in mice when compared with paclitaxel. For example, paclitaxel at its optimum dose (20 mg/kg) caused neither complete nor partial regressions in any of 10 mice in a Madison 109 (M109) s.c. lung tumor model, whereas DHA-paclitaxel caused complete regressions that were sustained for 60 days in 4 of 10 mice at 60 mg/kg, 9 of 10 mice at 90 mg/kg, and 10 of 10 mice at the optimum dose of 120 mg/kg. The drug seems to be inactive as a cytotoxic agent until metabolized by cells to an active form. The conjugate is less toxic than paclitaxel, so that 4.4-fold higher molar doses can be delivered to mice. DHA-paclitaxel in rats has a 74-fold lower volume of distribution and a 94-fold lower clearance rate than paclitaxel, suggesting that the drug is primarily confined to the plasma compartment. DHA-paclitaxel is stable in plasma, and high concentrations are maintained in mouse plasma for long times. Tumor targeting of the conjugate was demonstrated by pharmacokinetic studies in M109 tumor-bearing mice, indicating an area under the drug concentration-time curve of DHA-paclitaxel in tumors that is 8-fold higher than paclitaxel at equimolar doses and 57-fold higher at equitoxic doses. At equimolar doses, the tumor area under the drug concentration-time curve of paclitaxel derived from i.v. DHA-paclitaxel is 6-fold higher than for paclitaxel derived from i.v. paclitaxel. Even at 2 weeks after treatment, 700 nM paclitaxel remains in the tumors after DHA-paclitaxel treatment. Low concentrations of DHA-paclitaxel or paclitaxel derived from DHA-paclitaxel accumulate in gastrocnemius muscle; which may be related to the finding that paclitaxel at 20 mg/kg caused hind limb paralysis in nude mice, whereas DHA-paclitaxel caused none, even at doses of 90 or 120 mg/kg. The dose-limiting toxicity in rats is myelosuppression, and, as in the mouse, little DHA-paclitaxel is converted to paclitaxel in plasma. Because DHA-paclitaxel remains in tumors for long times at high concentrations and is slowly converted to cytotoxic paclitaxel, DHA-paclitaxel may kill those slowly cycling or residual tumor cells that eventually come into cycle.

Tumor targeting by conjugation of DHA to paclitaxel.

Targeting an anti-cancer drug to tumors should increase the Area Under the drug concentration-time Curve (AUC) in tumors while decreasing the AUC in normal cells and should therefore increase the therapeutic index of that drug. Anti-tumor drugs typically have half-lives far shorter than the cell cycle transit times of most tumor cells. Tumor targeting, with concomitant long tumor exposure times, will increase the proportion of cells that move into cycle when the drug concentration is high, which should result in more tumor cell killing. In an effort to test that hypothesis, we conjugated a natural fatty acid, docosahexaenoic acid (DHA), through an ester bond to the paclitaxel 2'-oxygen. The resulting paclitaxel fatty acid conjugate (DHA-paclitaxel) does not assemble microtubules and is non-toxic. In the M109 mouse tumor model, DHA-paclitaxel is less toxic than paclitaxel and cures 10/10 tumored animals, whereas paclitaxel cures 0/10. One explanation for the conjugate's greater therapeutic index is that the fatty acid alters the pharmacokinetics of the drug to increase its AUC in tumors and decrease its AUC in normal cells. To test that possibility, we compared the pharmacokinetics of DHA-paclitaxel with paclitaxel in CD2F1 mice bearing approximately 125 mg sc M109 tumors. The mice were injected at zero time with a bolus of either DHA-paclitaxel or paclitaxel formulated in 10% cremophor/10% ethanol/80% saline. Animals were sacrificed as a function of time out to 14 days. Tumors and plasma were frozen and stored. The concentrations of paclitaxel and DHA-paclitaxel were analyzed by LC/MS/MS. The results show that DHA targets paclitaxel to tumors: tumor AUCs are 61-fold higher for DHA-paclitaxel than for paclitaxel at equitoxic doses and eight-fold higher at equimolar doses. Likewise, at equi-toxic doses, the tumor AUCs of paclitaxel derived from i.v. DHA-paclitaxel are 6.1-fold higher than for paclitaxel derived from i.v. paclitaxel. The tumor concentration of paclitaxel derived from i.v. paclitaxel drops rapidly, so that by 16 h it has fallen to the same concentration (2.8 microM) as after an equi-toxic concentration of DHA-paclitaxel. In plasma, paclitaxel AUC after an MTD dose of DHA-paclitaxel is approximately 0.5% of DHA-paclitaxel AUC. Thus, the increase in tumor AUC and the limited plasma AUC of paclitaxel following DHA-paclitaxel administration are consistent with the increase in therapeutic index of DHA-paclitaxel relative to paclitaxel in the M109 mouse tumor model. A phase I clinical study has been completed at The Johns Hopkins Hospital to evaluate the safety of DHA-paclitaxel in patients with a variety of solid tumors. Twenty-one patients have been treated to date. The recommended phase II dose is 1100 mg/m(2), which is equivalent to 4.6 times the maximum approved paclitaxel dose on a molar basis. No alopecia or significant peripheral neuropathy, nausea, or vomiting have been observed. Asymptomatic, transient neutropenia has been the primary side effect. Eleven of 22 evaluable phase I patients transitioned from progressive to stable disease, as assessed by follow-up CT. Significant quality of life improvements have been observed. Thus, DHA-paclitaxel is well tolerated in patients and cures tumors in mice by targeting drug to tumors.

Fatty acid derivatives of clozapine: prolonged antidopaminergic activity of docosahexaenoylclozapine in the rat.

Stable amides of clozapine derived from fatty acids prominent in cerebral tissue might enhance the central activity of clozapine and reduce its exposure to peripheral tissues. Such derivatives might enhance the safety of this unique drug, which is the only agent with securely established superior antipsychotic effectiveness, but with a risk of potentially lethal systemic toxicity. Amide derivatives of clozapine were prepared from structurally varied fatty acid chlorides and evaluated for ability to inhibit behavioral arousal in rat induced by dopamine agonist apomorphine and to induce catalepsy. Their duration-of-action and potency were compared to free clozapine, and concentrations of clozapine were assayed in brain and blood. Selected agents were also evaluated for affinity at dopamine receptors and other potential drug-target sites. Clozapine-N-amides of linoleic, myristic, oleic, and palmitic acids had moderate initial central depressant activity but by 6 h, failed to inhibit arousal induced by apomorphine. However, the docosahexaenoic acid (DHA) derivative was orally bioavailable, 10-times more potent (ED(50) 5.0 micromol/kg) than clozapine itself, and very long-acting (>/= 24 h) against apomorphine, and did not induce catalepsy. DHA itself was inactive behaviorally. Clozapine showed expected dopamine receptor affinities, but DHA-clozapine was inactive at these and other potential target sites. After systemic administration of DHA-clozapine, serum levels of free clozapine were very low, and brain concentrations somewhat lower than after administering clozapine. DHA-clozapine is a long-acting central depressant with powerful and prolonged antidopaminergic activity after oral administration or injection without inducing catalepsy, and it markedly reduced peripheral exposure to free clozapine. It lacked the receptor-affinities shown by clozapine, suggesting that DHA-clozapine may be a precursor of free, pharmacologically active clozapine. Such agents may represent potential antipsychotic drugs with improved central/peripheral distribution, and possibly enhanced safety.

A pilot study of sexual lifestyle in a random sample of the population of Great Britain.

Rates of sexual-partner change and patterns of high-risk behaviour are important determinants of the spread of HIV. We carried out a survey to assess the feasibility of studying sexual lifestyle in a random sample of the British population, aged 16-64 years, in November 1987. Two thousand and seventy-seven households were selected using a multi-stage probability sampling procedure. Seven hundred and eight-five adults participated in a structured interview. The schedule included demographic details, attitudes to AIDS, numbers of sexual partners in different time periods, history of homosexuality and contact with prostitutes. An interview was obtained in 61% of households where contact was made, but the overall response rate was low (48%). There was marked variability between individuals in numbers of sexual partners in given time intervals. Men and women in younger cohorts had experienced first sexual intercourse earlier and had higher numbers of sexual partners than people in older cohorts. Surprisingly few reported high-risk behaviour such as homosexuality and use of prostitution. The methodological problems in trying to obtain unbiased and valid data on sexual behaviour are discussed. Further work is necessary to improve the response rate and questionnaire design.

Cultural factors and attrition in drug abuse treatment.

The present study examined how race related to attrition in drug abuse treatment. 165 male voluntary admissions to an inpatient Substance Abuse Unit were tested at admission on functioning, motivation, attitudes, symptoms, and mood-using reliable and valid scales. One week later they completed a 12-factor scale measuring perception of the treatment milieu. Data were analyzed in a 2 x 2 factorial design of analysis of variance. There were 106 White subjects and 59 Blacks. The dropout rate for Blacks and Whites was 63%. Two factors measured at intake, motivation and social functioning, showed statistically significant interactions between race and attrition. Four ward perception factors showed a differential effect related to race and attrition. The White dropout and completer did not differ in how they perceived the ward. Blacks, however, who perceived the environment as being more insightful, spontaneous, autonomous, and practical remained. Although Blacks and Whites differed on many variables, only six showed race-related differences in attrition. Having higher motivation and poorer adjustment influenced Whites to stay. Factors in the environment, however, influenced Blacks. What might be considered a more "therapeutic" milieu was effective in helping Blacks remain in treatment. Knowledge of these cultural differences could help in designing treatment programs.

Focus on the family as a factor in differential treatment outcome.

The prognostic relationship between prehospital living arrangements and treatment outcome was explored. Drug (N = 17) and alcohol (N = 19) patients who had lived with parents, wives, nonrelatives, or alone before voluntary admission to an inpatient substance abuse program were compared on changes in social dysfunctioning and symptomatology as a result of treatment. Ratings on each patient's level of dysfunctioning and symptomatology were made following intake into the program and within a 3-day period after receiving a regular discharge. While treatment had a positive effect on all groups, multivariate analysis of covariance showed a significant (P less than .009) differential rate of improvement between the pretreatment residential setting groups. Those who had lived alone or with nonrelatives prior to admission changed the most, becoming significantly less dysfunctional and symptomatic. Those coming from parental families changed the least improvement, while those who had lived with their spouses showed moderate improvement. Findings were consistent for both drug and alcohol patients. Results indicate that the type of home environment from which substance abusers come before engaging in treatment significantly influences their receptivity to rehabilitation. Findings suggest the need for assessment of the family environment and utilization of community resources as a means of enhancing adjustment.

The alcoholic's perception of the ward as a predictor of aftercare attendance.

The present study attempted to determine whether attendance in aftercare services could be predicted from the alcoholic's perception of the inpatient ward environment. Thirty-five Ss who completed inpatient treatment and were eligible for outpatient group therapy were followed up 3 months after discharge. One factor of the Ward Atmosphere Scale, autonomy, significantly differentiated attenders (N = 13) from nonattenders (N = 22); attenders perceived more autonomy on the ward than did nonattenders. Two additional factors, aggression and insight, also differentiated the groups, although not to a statistically significant degree. Attenders were found to perceive more encouragement by the staff to express openly their angry feelings and to share their personal selves with others than were nonattenders.

The total containment of a batch-type zonal centrifuge.

A batch-type zonal centrifuge has been modified and totally contained for use with biologically hazardous materials. A sealed cabinet encloses the centrifuge and the ancilliary equipment. It is operated with a flow of filtered air when the zonal system is on, decontaminated with ethylene oxide, and maintained at a negative pressure throughout. The centrifuge subsystems can be drained, flushed, and decontaminated with ethylene oxide before an engineer services the machine. The sample handling system within the cabinet is remotely controlled.